Method of forming nitride film

ABSTRACT

A method of forming a nitride film in a fine recess formed in a surface of a substrate to be processed, by repeating a process, which includes adsorbing a film forming raw material gas onto the substrate and nitriding the adsorbed film forming raw material gas. The nitriding the adsorbed film forming raw material gas includes converting a NH 3  gas as a nitriding gas, and an adsorption inhibiting gas for inhibiting adsorption of the NH3 gas into radicals and supplying the radicals onto the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefits of Japanese Patent Application Nos.2016-017022 and 2016-234902, filed on Feb. 1, 2016 and Dec. 2, 2016,respectively, in the Japan Patent Office, the disclosures of which areincorporated herein in their entirety by reference.

TECHNICAL FIELD

The present disclosure relates to a method of forming a nitride filmsuch as a silicon nitride film.

BACKGROUND

In a sequence of manufacturing a semiconductor device, there exists aprocess of forming a nitride film such as a silicon nitride film (SiNfilm) or the like, serving as an insulating film, on a semiconductorwafer represented by a silicon wafer. A chemical vapor deposition (CVD)method is employed for such a SiN film forming process.

When a SiN film (CVD-SiN film) is buried in a trench by means of the CVDmethod, the film tends to be thicker at the frontage of the trench thanat the bottom thereof and, as miniaturization of devices advances, voidsor seams in the film becomes problematic.

In contrast, an atomic layer deposition method (ALD method) is known asa technology capable of forming a film conformably in a fine trench witha better step coverage than the CVD method. The ALD method is also usedto bury a SiN film in the trench.

However, as the device miniaturization further advances, even ifconformal film formation using the ALD method is performed, it becomesdifficult to bury the SiN film in a trench while preventing voids orseams.

SUMMARY

Some embodiments of the present disclosure provide to a method offorming a nitride film, which is capable of burying a nitride film in afine recess while preventing voids or seams.

According to one of the embodiments, there is provided a method offorming a nitride film in a fine recess formed in a surface of asubstrate to be processed, by repeating a process including adsorbing afilm forming raw material gas onto the substrate; and nitriding theadsorbed film forming raw material gas, wherein the nitriding theadsorbed film forming raw material gas includes converting a NH₃ gas asa nitriding gas, and an adsorption inhibiting gas for inhibitingadsorption of the NH3 gas into radicals and supplying the radicals ontothe substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentdisclosure, and together with the general description given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present disclosure.

FIGS. 1A and 1B are views used to explain adsorption states of NH₃* in acase where only NH3* is supplied during nitridation and in a case whereboth of NH₃* and H₂* are supplied during nitridation.

FIG. 2 is a schematic graphical view showing a change in probability ofexistence of H₂* in a recess in a depth direction.

FIG. 3 is a sectional view schematically showing a film formation stateof a SiN film in a case where NH₃* and H₂* are supplied duringnitridation.

FIG. 4 is a sectional view showing a structure of a semiconductor waferused in a specific example of a method of forming a nitride film,according to one embodiment of the present disclosure.

FIG. 5 is a sectional view showing a state of a film forming process incarrying out the method of forming a nitride film, according to oneembodiment of the present disclosure.

FIG. 6 is a sectional view showing a state of a film forming process incarrying out the method of forming a nitride film, according to oneembodiment of the present disclosure, wherein FIG. 6 shows a state inwhich the film formation is further advanced from the state of FIG. 5.

FIG. 7 is a sectional view showing a state of a film forming process incarrying out the method of forming a nitride film, according to oneembodiment of the present disclosure, wherein it shows a state in whichburying of the film in a recess has been completed.

FIG. 8 is a cross-sectional view showing one example of a film formingapparatus used to carry out a film forming method of the presentdisclosure.

FIG. 9 is a longitudinal sectional view of the film forming apparatus ofFIG. 8, which is taken along line A-A′ in FIG. 8.

FIG. 10 is a plan view showing the film forming apparatus of FIG. 9.

FIG. 11 is an enlarged longitudinal sectional view showing a firstregion of the film forming apparatus of FIG. 9.

FIG. 12 is a bottom view showing a precursor gas introduction unitinstalled in the first region.

FIG. 13 is an enlarged longitudinal sectional view showing one nitridingregion in a second region of the film forming apparatus of FIG. 9.

FIG. 14 is a flowchart for explaining a processing operation of the filmforming apparatus of FIG. 9.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present disclosure. However,it will be apparent to one of ordinary skill in the art that the presentdisclosure may be practiced without these specific details. In otherinstances, well-known methods, procedures, systems, and components havenot been described in detail so as not to unnecessarily obscure aspectsof the various embodiments.

In the present disclosure, a nitride film is formed by an ALD method. Inone embodiment, a case where a silicon nitride film (SiN film) is formedas the nitride film will be described by way of an example.

Outline of Method of Forming Silicon Nitride Film

A substrate to be processed in which a recess such as a trench or a holeis formed in a surface of the substrate is prepared, and adsorption andnitridation of a Si precursor (film forming raw material gas) arerepeated for the substrate a predetermined number of times to form asilicon nitride film.

In the nitridation, a NH₃ gas as a nitriding gas and an H₂ gas as anadsorption inhibiting gas are activated by plasma or the like and thenitridation is performed with generated NH₃ radicals (NH³*) and H₂radicals (H₂*). Note that NH₃* and H₂* contain all radicals generated bythe NH₃ gas and radicals generated by the H₂ gas, respectively.

Since NH₃* is easily adsorbed to Si and its lifetime is relatively long,when only NH₃* is supplied, it is adsorbed, as an amino group (—NH₂), onthe entire inner wall of the recess and makes a nitriding reaction withthe film forming raw material gas, as shown in FIG. 1A. Consequently,conformal film formation (which may be referred to as deposition) isperformed.

In contrast, when H₂* is used in addition to NH₃* in the nitridation,H₂* inhibits adsorption of NH₃* to Si. Therefore, an adsorption site ofNH₃* decreases. Further, the adsorption inhibiting effect of H₂* islarger at the upper portion of the recess and is smaller at the bottomof the recess.

Therefore, in the case of using H₂* in addition to NH₃*, the adsorptionsite of NH₃* becomes relatively small at the upper portion of the recessand becomes relatively large at the bottom of the recess, as shown inFIG. 1B.

In this manner, because of its short lifetime, H2* can be used tocontrol the adsorption of NH₃* at the upper portion and bottom portionof the recess. FIG. 2 is a schematic graphical view showing a change inprobability of existence of H₂* in a recess of 200 nm at 40 nmφ in adepth direction. As shown in FIG. 2, the existence probability of H₂*decreases toward the bottom of the recess, which indicates that thelifetime of H₂* is short.

in this way, as the adsorption site of NH₃* becomes relatively small atthe upper portion of the recess and becomes relatively large at thebottom of the recess, the nitriding reaction of the Si precursor, whichis the film forming raw material gas, proceeds more easily at the bottomof the recess than the upper portion of the recess and the depositionrate of a SiN film becomes accordingly larger at the bottom of therecess than the upper portion of the recess. For this reason, as shownin FIG. 3, a V-shaped film is formed to be thicker at the bottom of therecess and thinner at the upper portion of the recess. Therefore, evenin a case of burying a film in a fine recess, it is possible toextremely effectively prevent a situation such as forming the film withvoids left inside the recess.

However, in order to effectively obtain such an effect, it is desirableto form a film by means of an apparatus in which H₂* is generatedimmediately above a substrate to be processed so that H₂* having a shortlifetime is not deactivated at the upper portion of the substrate, andis supplied onto the substrate.

Specific Example of Method of Forming Nitride Film

Hereinafter, a specific example of a method of forming a nitride filmaccording to one embodiment of the present disclosure will be describedwith reference to FIG. 4.

First, as shown in FIG. 4, a semiconductor wafer as a substrate to beprocessed (hereinafter simply referred to as a wafer) W in which aninsulating film (SiO₂ film) 201 is formed on a Si base body 200 and afine recess 202 is formed in the insulating film 201 is prepared. Atthis time, the fine recess 202 is a trench or a hole and its size isabout 20 to 100 nm in width or diameter, 50 to 1000 nm in height andabout 5 to 50 in aspect ratio. For example, the width is 30 nm, theheight is 300 nm and the aspect ratio is 10.

Next, formation of a SiN film on such a wafer W is started. At thistime, for example, the wafer W repeatedly passes through a Si precursoradsorption region for adsorbing a Si precursor as a raw material gas anda plurality of nitridation regions in which a process for nitriding theSi precursor is performed, and the Si precursor adsorption andnitridation are repeated a predetermined number of times. Gas separationby a separation gas is performed between the Si precursor adsorptionregion and the nitridation regions.

In the step of adsorbing the Si precursor, the Si precursor isconformably formed on the inner wall of the recess 202 with a molecularlayer level of extremely thin film. As the Si precursor, monosilane(SiH₄), disilane (Si₂H₆), monochlorosilane (MCS; SiH₃Cl), dichlorosilane(DCS; SiH₂Cl₂), trichlorosilane (TCS; SiHCl₃), silicon tetrachloride(STC; SiCl₄), hexachlorodisilane (HCD; Si₂Cl₆) or the like can be used.Of these, DCS can be suitably used.

In the nitridation, as described above, a NH₃ gas as a nitriding gas anda H₂ gas as an adsorption inhibiting gas are activated by plasma or thelike to be NH₃* and H₂*, respectively, which are supplied onto the waferW and are adsorbed into the recess 202. At this time, as describedabove, since the lifetime of H₂* is short, the adsorption inhibitingeffect is larger at the upper portion of the recess 202 and smaller atthe bottom of the recess 202. Therefore, an adsorption site of NH₃*becomes relatively small at the upper portion of the recess 202 andbecomes relatively large at the bottom of the recess 202.

Therefore, by repeating the adsorption and nitridation of the Siprecursor, a nitriding reaction of the Si precursor proceeds further atthe bottom of the recess 202 and, during the formation of the SiN film,as shown in FIG. 5, a V-shaped SiN film 203 is formed to be thicker atthe bottom of the recess 202 and thinner at the upper portion of thefine recess 202.

Since such a V-shaped film can be formed, when the film formation isfurther continued, the SiN film 203 grows bottom-up in the fine recess202. Accordingly, the SiN film 203 can be also formed on an upperportion of a side wall of the recess 202 to such an extent that thefrontage of the SiN film 203 is not narrowed, as shown in FIG. 6 and,finally, the SiN film 203 can be buried in the recess 202 in a statewhere no void or seam exists in the recess 202, as shown in FIG. 7.

An activation technique in the nitridation is not particularly limitedbut it may be preferable to adopt a technique for generating radicalsimmediately above a semiconductor wafer which is a substrate to beprocessed, and supplying H* having a short lifetime immediately abovethe semiconductor wafer W without being inactivated. The processing bysuch a method can be suitably performed by an RLSA® microwave plasmaprocessing apparatus.

In the nitridation, a rare gas such as an Ar gas, He gas, Xe gas, Negas, Kr gas or the like may be used as a plasma generation gas, adilution gas or the like.

As conditions on the above-described SiN film formation, the temperaturemay be in a range of 400 to 600 degrees C., specifically, 435 degreesC., and the pressure may be in a range of 66.6 to 1330 Pa, specifically,266 Pa (2 Torr). Further, a flow rate ratio (partial pressure ratio) ofthe NH₃ gas to the H₂ gas (NH₃/H₂) may be in a range of 0.01 to 0.1.NH₃/H₂ corresponds approximately to NH₃*/H₂*.

As the adsorption inhibiting gas, a N₂ gas, Ar gas, He gas, Xe gas, Negas, Kr gas or the like may be used in addition to the H₂ gas. Byconverting one of these gases into radicals and supplying the radicalsdirectly above the substrate, it is possible to obtain the sameadsorption inhibiting effect as the H₂ gas. However, H₂ gas ispreferable as the adsorption inhibiting gas. The Ar gas, He gas, Xe gas,Ne gas and Kr gas may be also used as a plasma gas, a dilution gas orthe like. However, when being used as the adsorption inhibiting gas,they are converted into radicals immediately above the wafer andsupplied to the substrate, which is different in supply form from a caseof using them as the plasma gas or the dilution gas.

Film Forming Apparatus

Next, one example of a film forming apparatus for carrying out themethod for forming a nitride film according to the above embodiment willbe described. In this example, a case where a SiN film is formed byusing a DCS gas as a Si precursor which is a raw material gas will bedescribed.

FIG. 8 is a cross-sectional view of a film forming apparatus accordingto this example. FIG. 9 is a longitudinal sectional view of the filmforming apparatus of FIG. 8, which is taken along line A-A′ in FIG. 8.FIG. 10 is a plan view of the film forming apparatus according to thisexample. FIG. 11 is an enlarged longitudinal sectional view showing afirst region of the film forming apparatus according to this example.FIG. 12 is a bottom view showing a precursor gas introduction unitinstalled in the first region. FIG. 13 is an enlarged longitudinalsectional view showing one nitriding region in a second region of thefilm forming apparatus according to this example.

As shown in FIGS. 8 to 11, the film forming apparatus has a vacuumcontainer 11 which defines a processing space where a film formingprocess is performed. In this vacuum container 11, disposed is a rotarytable 2 having a plurality of wafer mounting regions 21 formed thereon.A space above a portion of the vacuum container 11 through which therotary table 2 passes includes a first region R1 in which a Si precursoras a raw material gas is adsorbed on the wafer W and a second region R2in which the wafer W is subjected to nitridation. The second region R2includes three nitriding regions, i.e., a central nitriding region R2-1and nitriding regions R2-2 and R2-3 on both sides thereof. The sidenitriding regions R2-2 and R2-3 may be used as a pre-nitridation regionand a post-nitridation region, respectively.

A precursor gas introduction unit 3 for introducing the Si precursor,which is the raw material gas, into the first region R1 is disposedabove the first region R1 in the vacuum container 11. A precursor gassupply source 52 is connected to the precursor gas introduction unit 3.A NH₃ gas and a H₂ gas are supplied into the nitriding region R2-1 ofthe second region R2 from a NH₃ gas supply source 54 and a H₂ gas supplysource 55, respectively, via pipes from the outside and inside thereof.Although not shown in FIG. 9, similarly, the NH₃ gas and the H₂ gas aresupplied into the nitriding regions R2-2 and R2-3. In addition, plasmageneration parts 6A, 6B and 6C are disposed in the nitriding regionsR2-1, R2-2 and R2-3, respectively. The gas supply system and the plasmageneration parts will be described in more detail later.

As shown in FIG. 9, the vacuum container 11 is substantially a circularflat container composed of a container main body 13 forming the sidewall and the bottom of the vacuum container 11, and a ceiling plate 12for air-tightly closing an opening of the upper surface side of thecontainer main body 13. The vacuum container 11 is made of metal suchas, for example, aluminum, and the inner surface of the vacuum container11 is subjected to plasma treatment such as anodizing treatment orceramic spraying treatment.

For example, the surface of the rotary table 2 is subjected to the sameplasma treatment as in the vacuum container 11. A rotary shaft 14extending vertically downward is installed at the center of the rotarytable 2 and a rotary drive mechanism 15 for rotating the rotary table 2is provided at the lower end of the rotary shaft 14.

As shown in FIG. 8, six wafer mounting regions 21 are equally placed onthe top surface of the rotary table 2 in the circumferential direction.Each of the wafer mounting regions 21 is configured as a circular recesshaving a diameter slightly larger than that of the wafer W. The numberof wafer mounting regions 21 is not limited to six.

As shown in FIG. 9, an annular groove 45 is formed along thecircumferential direction of the rotary table 2 on the bottom of thecontainer main body 13 positioned below the rotary table 2. In thisannular groove 45, a heater 46 is installed so as to correspond to anarrangement region of the wafer mounting regions 21. The wafer NV on therotary table 2 is heated to a predetermined temperature by the heater46. In addition, an opening of the top surface of the annular groove 45is closed by a heater cover 47 which is an annular plate member.

As shown in FIGS. 8 and 10, a loading/unloading part 101 for loading andunloading the wafer W is installed in the side wall surface of thevacuum container 11. The loading/unloading part 101 can be opened andclosed by a gate valve. The wafer W held by an external transfermechanism is loaded into the vacuum container 11 via theloading/unloading part 101.

In the rotary table 2 as configured above, when the rotary table 2 isrotated by the rotary shaft 14, each wafer mounting region 21 isrevolved around the rotational center of the rotary table 2. At thattime, the wafer mounting region 21 passes through an annular revolutionregion R_(A) indicated by a one-dot chain line.

Next, the first region R1 will be described.

As shown in FIG. 9, the precursor gas introduction unit 3 in the firstregion R1 is installed at the bottom side of the ceiling plate 12 facingthe top surface of the rotary table 2. In addition, as shown in FIG. 8,the planar shape of the precursor gas introduction unit 3 is a fan shapeformed by partitioning the revolution region R_(A) of the wafer mountingregion 21 in a direction intersecting the direction of revolution of thewafer mounting region 21.

As shown by enlargement in FIGS. 11 and 12, the precursor gasintroduction unit 3 is structured to include a precursor gas diffusionspace 33 in which the precursor gas is diffused, an exhaust space 32 inwhich the precursor gas is exhausted, and a separation gas diffusionspace 31 in which a separation gas for separating the lower region ofthe precursor gas introduction unit 3 from the outer region of theprecursor gas introduction unit 3 is diffused, which are stacked in thisorder from the lower side.

The lowermost precursor gas diffusion space 33 is connected to theprecursor gas supply source 52 via a precursor gas supply path 17, anopen/close valve V1 and a flow rate controller 521. For example, as a Siprecursor which is a raw material gas, a DCS gas is supplied from theprecursor gas supply source 52. A large number of discharge holes 331for supplying the precursor gas from the precursor gas diffusion space33 toward the rotary table 2 are formed in the bottom surface of theprecursor gas introduction unit 3.

The discharge holes 331 are distributed in a fan-shaped region indicatedby a broken line in FIG. 12. The length of two sides of the fan-shapedregion extending in the radial direction of the rotary table 2 is longerthan the diameter of the wafer mounting region 21. Therefore, when thewafer mounting region 21 passes below the Si precursor introduction unit3, the Si precursor as the raw material gas is supplied from thedischarge holes 331 onto the entire surface of the wafer W mounted inthe wafer mounting region 21.

The fan-shaped region provided with the large number of discharge holes331 constitutes a discharge part 330 of a film forming precursor gas. Aprecursor gas supply part is constituted by the discharge part 330, theprecursor gas diffusion space 33, the precursor gas supply path 17, theopen/close valve V1, the flow rate controller 521 and the precursor gassupply source 52.

As shown in FIGS. 11 and 12, the exhaust space 32 formed above theprecursor gas diffusion space 33 communicates with an exhaust port 321extending along a closed path surrounding the discharge part 330. Inaddition, the exhaust space 32 is connected to an exhaust mechanism 51via an exhaust path 192 and has an independent flow path which leads theprecursor gas, which is supplied below the precursor gas introductionunit 3 from the precursor gas diffusion space 33, to the exhaustmechanism 51. An exhaust part is constituted by the exhaust port 321,the exhaust space 32, the exhaust path 192 and the exhaust mechanism 51.

Further, the separation gas diffusion space 31 formed above the exhaustspace 32 communicates with a separation gas supply port 311 extendingalong a closed path surrounding the exhaust port 321. Further, theseparation gas diffusion space 31 is connected to a separation gassupply source 53 via a separation gas supply path 16, an open/closevalve V2 and a flow rate controller 531. A separation gas whichseparates the inside and outside atmospheres of the separation gassupply port 311 and which also functions as a purge gas for removing theprecursor gas excessively adsorbed onto the wafer W is supplied from theseparation gas supply source 53. As the separation gas, an inert gassuch as an Ar gas is used. A separation gas supply part is constitutedby the separation gas supply port 311, the separation gas diffusionspace 31, the separation gas supply path 16, the open/close valve V2,the flow rate controller 531 and the separation gas supply source 53.

In the precursor gas introduction unit 3, the precursor gas suppliedfrom each discharge hole 331 of the discharge part 330 spreads aroundwhile flowing over the rotary table 2, eventually reaches the exhaustport 321 and is exhausted from the top surface of the rotary table 2.Therefore, in the vacuum container 11, a region where the precursor gasis present is limited to the inside of the exhaust port 321 disposedalong a first closed path. Since the precursor gas introduction unit 3has a shape in which a part of the revolution region R_(A) of the wafermounting region 21 is partitioned in a direction intersecting with therevolution direction of the wafer mounting region 21, when the rotarytable 2 is rotated, the wafer W mounted in each wafer mounting region 21passes through the first region R1 and the precursor gas is adsorbedonto the entire surface of the wafer W.

On the other hand, around the exhaust port 321, the separation gassupply port 311 is disposed along a second closed path and a separationgas is supplied from the separation gas supply port 311 toward the topsurface of the rotary table 2. Therefore, the inside and outside of thefirst region R1 are doubly separated by the exhaust gas from the exhaustport 321 and the separation gas supplied from the separation gas supplyport 311 thereby effectively preventing leakage of the precursor gas tothe outside of the first region R1 and introduction of a reaction gascomponent from the outside of the first region R1.

The range of the first region R1 may be a range in which a sufficientcontact time can be secured for adsorbing the precursor gas on theentire surface of the wafer W and in which the first region R1 does notinterfere with the second region R2 in which the nitridation isperformed, the second region R2 being formed outside the first regionR1.

Next, the second region R2 will be described. As described above, thesecond region R2 has three nitriding regions R2-1, R2-2 and R2-3provided with the respective plasma generation parts 6A, 6B and 6C. TheNH₃ gas and the H₂ gas are supplied from the NH₃ gas supply source 54and the H₂ gas supply source 55 from the outside and inside thereof viapipes.

As shown in FIG. 13, the plasma generation part 6A of the nitridingregion R2-1 includes an antenna part 60 which radiates a microwavetoward the inside of the vacuum container 11, a coaxial waveguide 65which supplies a microwave toward the antenna part 60, and a microwavegenerator 69, and is configured with an RLSA® microwave plasmaprocessing apparatus. The antenna part 60 is installed so as to close atriangular opening formed in the ceiling plate 12 facing the top surfaceof the rotary table 2.

The microwave generator 69 generates a microwave having a frequency of,for example, 2.45 GHz. A waveguide 67 is connected to the microwavegenerator 69 and a tuner 68 for impedance matching is installed in thewaveguide 67. The waveguide 67 is connected to a mode converter 66 andthe coaxial waveguide 65 extending downward is connected to the modeconverter 66. In addition, the antenna part 60 is connected to the lowerend of the coaxial waveguide 65. Then, the microwave generated by themicrowave generator 69 propagates to the antenna part 60 via thewaveguide 67, the mode converter 66 and the coaxial waveguide 65. Themode converter 66 converts a mode of the microwave into a mode capableof guiding the microwave to the coaxial waveguide 65. The coaxialwaveguide 65 has an inner conductor 651 and an outer conductor 652coaxial with the inner conductor 651.

The antenna part 60 is configured with an RLSA® antenna including adielectric window 61, a planar slot antenna 62, a retardation member 63and a cooling jacket 64.

The planar slot antenna 62 is configured h an approximately triangularmetal plate and has a number of slots 621 formed therein. The slots 621are appropriately set so as to radiate the microwave efficiently. Forexample, the slots 621 are arranged at predetermined intervals in theradial direction from the center of the above-mentioned triangular shapeto the periphery thereof and in the circumferential direction and areformed such that adjacent slots 621 and 621 intersect with each other orare orthogonal to each other.

The dielectric window 61, which is made of ceramics such as alumina, hasa function to pass the microwave therethrough, which is transmitted fromthe coaxial waveguide 65 and radiated from the slots 621 of the planarslot antenna 62, and to generate surface wave plasma uniformly in aspace above the rotary table 2. The dielectric window 61 is made, e.g.,ceramics such as alumina or the like, and has a triangular planar shapecapable of blocking the opening of the ceiling plate 12. An annularrecess 611 having a tapered surface for stably generating plasma byconcentrating microwave energy is formed in the bottom surface of thedielectric window 61. The bottom surface of the dielectric window 61 maybe planar.

The retardation member 63 is installed on the planar slot antenna 62 andis made of a dielectric material having a dielectric constant largerthan that of vacuum, for example, ceramics such as alumina. Theretardation member 63 is provided to shorten the wavelength of themicrowave and has substantially a triangular planar shape correspondingto the dielectric window 61 and the planar slot antenna 62. The coolingjacket 64 is installed on the retardation member 63. A coolant flow path641 is formed inside the cooling jacket 64 and the antenna part 60 canbe cooled by flowing a coolant through the coolant flow path 641.

Then, the microwave generated by the microwave generator 69 passesthrough the slot 621 of the planar slot antenna 62 via the waveguide 67,the mode converter 66, the coaxial waveguide 65 and the retardationmember 63 and is supplied to a space S immediately above the wafer Wunder the dielectric window 61 through the dielectric window 61.

A plurality of (e.g., 2) peripheral side gas discharge holes 703 fordischarging a gas for nitridation into the space S where plasma isgenerated are formed in the periphery of a portion supporting thedielectric window 61 of the ceiling plate 12. The peripheral side gasdischarge holes 703 are arranged with a space therebetween. Theperipheral side gas discharge holes 703 communicate with a peripheralside gas supply path 184 opened to the top surface of the ceiling plate12. A pipe 562 is connected to the peripheral side gas supply path 184.The NH₃ gas supply source 54 and the H₂ gas supply source 55 areconnected to the pipe 562 via a pipe 544 and a pipe 554. An open/closevalve V4 and a flow rate controller 542 are installed in the pipe 544and an open/close valve V6 and a flow rate controller 552 are installedin the pipe 554.

On the other hand, a central side gas discharge hole 704 for discharginga gas for nitridation into the space S where plasma is generated isformed in the center of the portion supporting the dielectric window 61of the ceiling plate 12. The central side gas discharge hole 704communicates with a central side gas supply path 185 opened to the topsurface of the ceiling plate 12. A pipe 561 is connected to the centralside gas supply path 185. The NH₃ gas supply source 54 and the H₂ gassupply source 55 are connected to the pipe 561 via a pipe 543 and a pipe553. An open/close valve V3 and a flow rate controller 541 are installedin the pipe 543 and an open/close valve V5 and a flow rate controller551 are installed in the pipe 553. These components constitute anitriding gas supply part.

Thus, the NH₃ gas and the H₂ gas are supplied into the space Simmediately above the wafer (W) passing region into which the microwaveis supplied and NH₃* and H₂* are generated in a region immediately abovethe wafer (W) passing region.

Note that a separate gas supply line may be provided to supply a raregas such as an Ar gas, as a plasma generation gas, to a positionimmediately under the dielectric window 61.

The plasma generation parts 6B and 6C of the other nitriding regionsR2-2 and R2-3 are also configured exactly in the same manner as theplasma generation part 6A of the above-described nitriding region R2-1.The supply of the NH₃ gas and the H₂ gas from the NH₃ gas supply source54 and the H₂ gas supply source 55 in the nitriding regions R2-2 andR2-3 is also performed in the same manner as that in the nitridingregion R2-1.

The processing space of the second region R2 in which the nitridation isperformed is exhausted by the exhaust mechanism 56 via four exhaustports 190A, 190B, 190C and 190D uniformly installed in the outer edge ofthe bottom of the container main body 13 of the vacuum container 11, asshown in FIG. 8.

As shown in FIG. 8, the film forming apparatus includes a control part8. The control part 8 is constituted by a computer having a CPU and astorage part and controls various components of the film formingapparatus, for example, the rotary drive mechanism 15 for rotating therotary table 2, the precursor gas supply part, the separation gas supplypart, the nitriding as supply part, the plasma generation parts 6A to6C, and the like. A control program for giving instructions to thevarious components for executing a predetermined film forming processwith the film forming apparatus, that is, process recipes, variousdatabases and the like are stored in the storage part. The processrecipes and the like are stored in a storage medium. The storage mediummay be a hard disk built in the computer or may be a portable mediumsuch as a CD ROM, a DVD, a semiconductor memory or the like. Further,the process recipes and the like may be transmitted from another devicevia an appropriate line.

Next, the processing operation of the film forming apparatus configuredas above will be described with reference to a flow chart of FIG. 14.

First, the gate valve of the loading/unloading part 101 is opened and awafer W is loaded into the vacuum container 11 by an external transfermechanism and is mounted on the wafer mounting region 21 of the rotarytable 2 (Step S1). The transfer of the wafer W is performed byintermittently rotating the rotary table 2 and wafers W are mounted onall of the wafer mounting regions 21. When the mounting of the wafers Wis completed, the transfer mechanism is retracted and the gate valve ofthe loading/unloading part 101 is closed. At this time, the interior ofthe vacuum container 11 is evacuated to a predetermined pressure inadvance by the exhaust mechanisms 51 and 56. In addition, as theseparation gas, for example, an Ar gas is supplied from the separationgas supply port 311.

Thereafter, the temperature of the wafer W is raised to a predeterminedset temperature by the rotary table 2 set at a predetermined temperaturein a range of 400 to 600 degrees C. by the heater 46 based on adetection value of a temperature sensor (not shown) (Step S2).

At the point of time when the wafer W reaches the predetermined settemperature, supply of a Si precursor into the first region R1 in thevacuum container 11, supply of a NH₃ gas and a H₂ gas for nitridationinto the second region R2, and supply of a microwave from the plasmageneration parts 6A to 6C are started (Step S3).

Thereafter, the rotary table 2 is rotated in a clockwise direction at apreset rotation speed and a film forming process is performed (Step S4).

At this time, as the Si precursor, which is a raw material gas, a DCSgas is supplied into the first region R1 from the discharge part 330 ofthe precursor gas introduction unit 3 in a range of flow rate of, forexample, 600 to 1200 sccm and the NH₃ gas and the H₂ gas for nitridationare supplied into second region R2 from the peripheral side gasdischarge holes 703 and the central side gas discharge hole 704 of thenitriding regions R2-1, R2-2 and R2-3 in a range of flow rate of, forexample, 10 to 1000 sccm and 2000 to 8000 sccm respectively. By turningon the microwave generator 69 of the plasma generation parts 6A to 6C, amicrowave is supplied into the space S immediately above the wafer (W)passing region. At that time, the internal pressure of the vacuumcontainer 11 is set to fall within a range of, for example, 66.6 to 1330Pa. Further, the microwave power is set to, for example, 1000 to 2500 W.

Thus, in the vacuum container 11, in the first region R1, the precursorgas supplied from the discharge part 330 of the precursor gasintroduction unit 3 is flown into a limited region up to the exhaustport 321 surrounding the discharge part 330. On the other hand, in thesecond region R2, the NH₃ gas and the H₂ gas discharged from theperipheral side gas discharge holes 703 and the central side dischargehole of the nitriding regions R2-1, R2-2 and R2-3 are converted intoNH₃* and H₂*, respectively, by being converted into plasma by themicrowave supplied from the antenna part 60 of the plasma generationparts 6A, 6B and 6C, which are exhausted from the exhaust ports 190A,19013, 190C and 190D. In addition, the atmosphere in the first region R1and the atmosphere in the second region R2 are separated from each otherby the separation gas.

In this manner, when the DCS gas which is the raw material gas (Siprecursor) is supplied into the first region R1 and the NH₃* and H₂* aresupplied into the second region R2, the wafer W mounted in each wafermounting region 21 of the rotary table 2 alternately repeatedly passesthrough the first region R1 and the second region R2 as the rotary table2 is rotated. Thus, the DCS gas as the precursor gas, the Ar gas as theseparation gas (purge gas), the NH₃* and H₂* and the Ar gas as theseparation gas (purge gas) are sequentially supplied onto the wafer W, aSiN film is formed by the film farming technique based on the ALDmethod, and the SiN film is buried in the fine trench formed in thewafer W. Then, at the point of time when the number of rotations of therotary table 2 reaches a predetermined number of times, the burying ofSiN is ended.

At this time, in the second region R2, in each of the nitriding regionsR2-1, R2-2 and R2-3, plasma is generated by the microwave in each of theplasma generation parts 6A, 6B and 6C, the NH₃ gas as a nitriding gasand the H₂ gas as an adsorption inhibiting gas are excited into NH₃* andH₂*, respectively, by the plasma, which are supplied onto the wafer W.At this time, since the NH₃* and H₂* are generated immediately above thewafer (W) passing region in each of the nitriding regions R2-1, R2-2 andR2-3, the H₂* having a short lifetime is also supplied onto the wafer Wwhile maintaining the state of H₂*.

On the other hand, as described above, since the lifetime of H₂* isshort, the adsorption inhibiting effect of H₂* is larger at the upperportion of the trench and smaller at the bottom of the trench. For thisreason, the adsorption site of NH₃* becomes relatively small at theupper portion of the recess and becomes relatively large at the bottomportion of the recess.

Therefore, in the process of depositing the SiN film, the nitridingreaction of DCS as the film forming raw material is more likely toproceed at the bottom of the trench than at the upper portion of thetrench, the film formation proceeds in a state where the film maintainsa V shape, thereby making it possible to bury the SiN film in the trenchin the absence of voids and seams.

Further, since the film forming apparatus can perform the film formingprocess on a plurality of waters at one time, a throughput is high.

Other Applications

Although the embodiments of the present disclosure have been describedabove, the present disclosure is not limited to the above embodiments,but various modifications can be made without departing from the spiritof the invention.

For example, the case where the silicon precursor and NH₃* and H₂* areused to form the silicon nitride film has been described by way ofexample in the above embodiment, but the present disclosure is notlimited to this case but may be applied to any case where a nitride filmis formed by NH₃* and H₂*. For example, the present disclosure may beapplied to various nitride films, such as a case where a TiN film isformed using a Ti precursor, a case where a BN film is formed using a Bprecursor, a case where a WN film is formed using a W precursor, etc.

Also, the film forming apparatus is not limited to those exemplifiedabove but may be any apparatus as long as it can supply H₂* radicalsonto a substrate to be processed without deactivating the radicals. Inaddition, the case where the rotary table on which a plurality of wafersare mounted is rotated to pass the wafers through the first region wherethe precursor gas is adsorbed and the second region R2 where thenitridation is performed to form a nitride film has been described inthe above embodiment. However, it is also possible to use a single wafertype film forming apparatus in which supply, purge, nitridation andpurge of a precursor gas are repeated.

According to the present disclosure in some embodiments, in forming anitride film in a fine recess by repeating a first step of adsorbing afilm forming raw material gas and a second step of nitriding theadsorbed film forming raw material gas, the second step is performed byconverting a NH₃ gas as a nitriding gas and an adsorption inhibiting gaswhich inhibits adsorption of the NH₃ gas into radicals and supplyingthem onto a substrate to be processed. At this time, by using a gasincluding radicals having short lifetime as the adsorption inhibitinggas, it is possible to provide less adsorption inhibition gas radicalsat the bottom of the recess than at the upper portion of the recess andto increase the adsorption amount of NH₃ radicals at the bottom of therecess. Therefore, it is possible to proceed with film formation in aV-shaped recess which is thicker at the bottom of the recess and thinnerat the upper portion of the recess and it is possible to bury a nitridefilm in a state in which voids or seams are not present in the recess.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A method of forming a nitride film in a finerecess formed in a surface of a substrate to be processed, by repeatinga process comprising: adsorbing a film forming raw material gas onto thesubstrate; and nitriding the adsorbed film forming raw material gas,wherein the nitriding the adsorbed film forming raw material gasincludes converting a NH₃ gas as a nitriding gas, and an adsorptioninhibiting gas for inhibiting adsorption of the NH3 gas into radicalsand supplying the radicals onto the substrate.
 2. The method of claim 1,wherein a H2 gas is used as the adsorption inhibiting gas.
 3. The methodof claim 2, wherein a flow rate ratio NH₃/H₂ of the NH₃ gas to the H₂gas falls within a range of 0.01 to 0.1.
 4. The method of claim 1,wherein the converting into radicals is performed by generatingmicrowave plasma immediately above the substrate.
 5. The method of claim1, wherein the adsorbing a film forming raw material gas and thenitriding the adsorbed film forming raw material gas are performed byproviding a first region in which the adsorbing a film forming rawmaterial gas is performed and a second region in which the nitriding theadsorbed film forming raw material gas is performed, in a vacuumcontainer and revolving a plurality of substrates to be processed, whichare mounted on a rotary table in the vacuum container, so that thesubstrates to be processed sequentially pass through the first regionand the second region.
 6. The method of claim 1, wherein a Si precursoris used as the film forming raw material gas to form a silicon nitridefilm.